Abstract. The rates at which ozone-depleting substances (ODSs) are removed from the
atmosphere, which determine the lifetimes of these ODSs, are key factors for
determining the rate of ozone layer recovery in the coming decades. We
present here a comprehensive uncertainty analysis of future mixing ratios of
ODSs, levels of equivalent effective stratospheric chlorine (EESC), ozone
depletion potentials, and global warming potentials (GWPs), using, among other
information, the 2013 WCRP/SPARC (World Climate Research Programme/Stratospheric
Processes and their Role in Climate) assessment of lifetimes of ODSs and their
uncertainties. The year EESC returns to pre-1980 levels, a metric commonly
used to indicate a level of recovery from ODS-induced ozone depletion, is
2048 for midlatitudes and 2075 for Antarctic conditions based on the
lifetimes from the SPARC assessment, which is about 2 and 4 yr,
respectively, later than based on the lifetimes from the WMO (World Meteorological Organization) assessment of
2011. However, the uncertainty in this return to 1980 levels is much larger
than the shift due to this change in lifetimes. The year EESC returns to
pre-1980 levels ranges from 2039 to 2064 (95% confidence interval) for
midlatitudes and from 2061 to 2105 for the Antarctic spring. The primary
contribution to these ranges comes from the uncertainty in the lifetimes,
with smaller contributions from uncertainties in other modeled parameters.
The earlier years of the return estimates derived by the uncertainty
analysis, i.e., 2039 for midlatitudes and 2061 for Antarctic spring, are
comparable to a hypothetical scenario in which emissions of ODSs cease in
2014. The later end of the range, i.e., 2064 for midlatitudes and 2105 for
Antarctic spring, can also be obtained by a scenario with an additional
emission of about 7 Mt CFC-11 eq. (eq. – equivalent) in 2015, which is the same as about 2 times
the projected cumulative anthropogenic emissions of all ODSs from 2014 to
2050, or about 12 times the projected cumulative HCFC emissions from 2014 to
2050.